Wow - I was doing almost the same routine as you up until 9 months. Actually, its really nice to read that as I remember it being a really hard time. I didn't feel like there was enough detail in the advice I was given to start weaning DD. It just felt like such a big step, although it wasn't for DD in the end - lol.
If you are keen to wean down to 1 feed by 12 months, then from now is a good time to start. I would pick one particular feed, for example, the 3.30pm and simply don't offer any boozie. Offer bubs a snack and sippy cup or bottle (water, juice - what ever you want) instead.
Initially I tried not to do any-thing at that feed time that would make DD think it was boobie time, such as sitting her in her high chair and feeding her some custard. To be honest, she didn't seem to care. She was just as happy getting her snack and then playing.
I let that new routine settle in over a week (or so) then picked another feed to drop. Once again, I offered DD a snack instead.
I'm not sure if you give your bub a BF before day naps, I did. I left weaning those feeds to last. DD was about 11 months then, so I offered her a small drink of warm cows milk instead of boozie. It worked really well, although did take DD a couple of days to adjust. You could try formula then or even water or juice, it doesn't have to be cows milk as its not recommended until 12 months.
By 9 months when I started to wean DD was having 3 solid meals pretty much around our routine. That is breakfast around 7.30am, lunch around 12pm and dinner around 5.30pm. I introduced an afternoon and morning snack when weaning DD which works out about 9am and 3.30pm.
Best of luck, I hope you reach your goal by 12 months (ish). I'm on 1 BF a night now (before bed time) and its going along really well.
DD is 3yr 8 months - DS is 6 months